The present invention relates to a blast joint suitable for service in production zones where the joint is subjected to high speed particle impingement.
Blast joints are used in the production zones of oil and gas wells in order to protect the production tubing string against the abrasive environments, such as e.g. high speed particle (sand grains) impingement.
Particularly, in formations producing high pressure gas, the flow into the well bore is at high velocities. The fluid stream containing abrasive materials impinges on the production tubing causing its abrasion and erosion. In these situations, it is desirable to protect the production tubing. Many different efforts have been made to solve the problem of the erosion due to producing fluids.
The blast joints known in the prior art include a series of elements, such as protection rings made of abrasive resistant materials, mounted about a tubular member U.S. Pat. Nos. 4,381,821; 4,028,796). The elements are supported on the tubular member and compressed together by different kinds of support means (e.g., cover rings in U.S. Pat. No. 4,889,185) thereby forming a coupling shield around the tubular member.
U.S. Pat. No. 5,549,333 discloses in addition the use of elastomer spacer rings which held carbide protection rings to maintain them in end-to-end contact to fully protect the tubing string against erosion from the incoming fluids and particles; as well as permit movement of the carbide protection rings during assembly installation and operation of the blast joint.
The abrasive resistant material used in the art is comprised of cemented tungsten carbide.
U.S. Pat. No. 5,369,579 discloses an electric blast control system incorporating an elongated instrument body including a plurality of electronic control modules which sense programmed well conditions such as fluid temperature and hydrostatic pressure, motion of the instrument body as it traverses the well bore. The electronic control modules provide electric logic pulses to a central processing unit, which define safe and unsafe parameters for downhole blasting operations.
With the evolution of new completion technologies, such as the use of hydraulic and electric power within the blast joints, the design of conventional blast joints is no more sufficient. In fact, the tools used recently downhole (e.g. ICVs: Interval Control Valves), require to be remotely operated via hydraulic and/or electric lines and this requires the integrity of the mentioned control lines and the production tubing for their expected life time cycle.
It is therefore an object of the present invention to provide a blast joint assembly which can be used for integral prevention of erosion of a production string crossing a production zone and simultaneous protection of hydraulic, electric and/or optical lines which need to cross same zones to operate and retrieve data from downhole operated tools.
Another object of the present invention is to provide a blast joint assembly which can be assembled and aligned in a simple way from modular starting joint elements in a short period of time and which withstands the highly corrosive and/or high temperature environments of the well bores.
A further object of the present invention is to provide a blast joint assembly which allows to cross perforated levels granting a reliable transmission of hydraulic and/or electric power between remote operated tools and controls placed on opposite sites of a perforation set.
These objects have been obtained by a blast joint assembly according to the present invention comprising at least one tubular joint body having at least one longitudinal slot on its outer surface, at least one series of protecting cover (shielding the longitudinal slot(s) to protect the control lines housed in the slot(s)) and structure for retaining the protecting cover on the joint body.
Any desired length of blast joint assembly can be assembled from modular tubular joint bodies according to the present invention by making up the ends of two or more tubular joint bodies, which are suitably threaded so to obtain a metal to metal high precision and very tough shoulder connection.